A number of portable, consumer devices are becoming available that make measurements of an analyte in a liquid sample such as blood or urine based upon an electrochemical measurement. A representative example of such devices is a glucose test meter, in which the user applies a small drop of blood to a test strip to obtain an indication of blood glucose level. In these devices, a single use test strip containing electrodes and reagents is inserted in a reusable meter that contains the electronics and the power supply (for example a battery) for making the measurement and displaying the results. In order to be acceptable to the consumer, the meter must be small, light-weight, and relatively inexpensive.
One of the challenges facing designers of meters of this type is providing reliable results in the face of varying conditions. It is desirable for the signal produced by the meter to be the same, regardless of the age of the battery, the ambient temperature, variability in the electronic circuits, or other loads that may be placed on the system such as when a display back lit display is in use.